تغییر در هذیان با تغییر در "جهش به نتایج" همراه است

Evidence has been put forward that premature termination of data collection and jumping to conclusions behavior (JTC) is associated with delusions. However, few investigations have attempted to track associations between changes in delusions and changes in JTC measures. In the current study individuals with schizophrenia spectrum disorders completed a version of the JTC task (involving fishing from lakes as opposed to drawing beads from a jar) at two timepoints 12 weeks apart. The results revealed significant negative correlations between change in task performance (number of requested pieces of information) and change in delusion scores over time. This evidence is consistent with the contention that the JTC task is sensitive to the cognitive systems underlying delusions in schizophrenia spectrum disorders.

Delusions are consensually defined as fixed false beliefs not amenable to contrary evidence, and are hallmark symptoms of schizophrenia spectrum disorders. Although it was initially proposed that delusional ideation cannot be explained by a pathology of reasoning (Maher, 1988), recent work has revealed a number of aberrations in reasoning in individuals with schizophrenia with current or past delusional ideas (Bell et al., 2006, Blackwood et al., 2001, Davies et al., 2001 and Garety and Freeman, 1999). One of the most commonly studied reasoning paradigms is known as the jumping to conclusions (JTC; Garety et al., 1991 and Huq et al., 1988) paradigm, and is widely cited and reviewed (Bell et al., 2006, Blackwood et al., 2001, Davies et al., 2001 and Garety and Freeman, 1999). JTC paradigms typically involve the beads task, where the subject is presented with jars containing beads of two colours (e.g., black and white beads divided 60–40 in one jar and 40–60 in the other) and are asked from which jar beads are being drawn when the jars have been hidden from view. Individuals with schizophrenia tend to request fewer beads before deciding on which jar is the source of the beads (draws-to-decision procedure). The dominant interpretation of this finding is that individuals with schizophrenia display a data gathering bias, in that they seek less information before reaching a decision (Garety and Freeman, 1999). However, the literature on whether or not JTC correlates with delusions is mixed, as a JTC bias has been observed for both currently deluded and non-deluded individuals with schizophrenia (Menon et al., 2006 and Moritz and Woodward, 2005), and in some studies an association with delusions is absent (McKay et al., 2007 and Young and Bentall, 1997). Some studies report that the association with delusions depends on methodological variables, such as the requirement to self-terminate the trial by indicating that they have enough information to decide (Garety et al., 1991, Moritz and Woodward, 2005 and van Dael et al., 2006), and/or high working memory load (i.e., the jars are hidden from view and the bead is replaced in the jar after being viewed; Menon et al., 2006). Unfortunately cross sectional studies cannot provide definitive evidence for the cognitive underpinnings of delusions, for two main reasons. First, between-group comparisons of conditions (e.g., delusional vs. nondelusional individuals) are less powerful than within-group comparisons, because any differences between the subjects contribute to the error term in the between-group design, but much of this source of error is subtracted out of the error term when each subject is used as his or her own control. Second, individuals currently displaying delusions may tend to possess certain characteristics that would not change if the delusions were to go into remission, such as a genetic predisposition that affects cognitive performance and/or a pre-existing cognitive style. A longitudinal study is more powerful and interpretable, because pre-existing differences between nondelusional and delusional conditions will be held constant as delusions change. This is feasible because delusions change in their severity over time in response to treatment, or spontaneously (Eaton et al., 1995, Gunduz-Bruce et al., 2005, Lieberman et al., 1993 and Sherwood et al., 2006). A computational model of JTC behavior (Moore and Sellen, 2006), for which a gain parameter was employed to model increases and decreases in dopamine levels in delusional individuals, predicted that changes in delusions should correspond with changes in JTC behavior. Longitudinal studies investigating the association of change in JTC with change in delusions over time have been carried out in the past using the beads task, with mixed results. In a recent longitudinal study, a JTC pattern in delusional individuals was stable over time despite improving symptomatology (Peters and Garety, 2006). A different study found that although performance on a beads task predicted subsequent change in positive symptoms, non-significant correlations between changes in task performance and changes in symptomatology were observed (Menon et al., 2008). Although both of these studies employed the draws-to-decision procedure, only one and two series of beads, respectively, were administered, leading to less stable JTC estimates compared to when multiple series are administered. In addition, in past studies our group has noted that individuals with schizophrenia have had difficulty comprehending the beads procedure (Moritz and Woodward, 2005). In order to increase comprehensibility of the task instructions, we developed a new JTC paradigm that involved a scenario of a fisherman fishing from two lakes, and developed a number of conditions that allowed four series of “beads” (or fish in this case) to be presented. We used this variation of the beads task (Huq et al., 1988) with a draws-to-decision procedure (Dudley et al., 1997, Fear and Healy, 1997, Menon et al., 2008 and Moritz and Woodward, 2005) in a longitudinal study involving pre- and post-assessment of a sample of individuals undergoing group cognitive behavioral therapy (CBT; Lecomte et al., 2008) or control treatments. According to an account holding that the JTC bias is a cognitive underpinning of delusions, we expected to observe a correlation between change in delusion scores and change in task performance, such that a decrease in JTC behavior should correspond with a decrease in delusions, and vice versa.

The mean number of requested catches at Time 1 and Time 2 is reported in Table 1 as a function of the four series conditions and direction of change in delusions. To investigate the impact of repeated testing sessions and series conditions, a 2 × 4 analysis of variance (ANOVA) was carried out, with Session (Time 1 and Time 2) and Series (Series 1, 2, 3 and 4) as within-subjects factors. This analysis revealed a significant Session effect, F(1,18) = 5.79, P < 0.05, but no significant Series effect, F(3,51) = 0.83, P = 0.48, and no significant Session × Series interaction, F(3,54) = 0.57, P = 0.64. The Series effect was characterized by decreasing conservativism over Time 1 and Time 2 (see Table 1). Adding direction of change in delusions as a between-subjects factor produced a 2 × 4 × 2 mixed-model ANOVA, and this resulted in a nonsignificant main effect for this factor, F(1,17) = 0.61, P = 0.54. This factor did not interact significantly with Session or Series (all Ps > 0.15).